When at 22,000 ft. cruise level in the vicinity of the Isle of Man, en route, on a scheduled flight from Birmingham Airport to Belfast City airport, sudden severe turbulence was encountered that disconnected the autopilot causing the aircraft to climb 500 ft. before manual control was assumed and the original cruise level regained. In the passenger cabin a crew member was thrown off her feet and suffering serious injuries, requiring hospital treatment, a passenger also suffered a minor injury .